Try starting with white noise, then add an LFO set to a random or triangle waveform as the amplitude modulator. Random will give you the best "throwing off sparks" or jumping live wire sound. Adjust the depth and rate to taste.

For a more static electrical sound, use a triangle, saw or square wave and add a slow LFO rate with medium depth and increase the rate til you can't discern the individual cycles. The faster the rate and deeper the wave trough, it will start to get a nice, nasty, yet unpitched buzz.

Make sure to set the filter flat and release time to zero, and leave the keyboard tracking on so you still get pitches. Play different patterns or clusters of notes til you hear what you want. A chorus or room ambience can give it a little animation if it feels too static and dry.